Cubic Feet to Liters — Conversion Guide for Tanks, Heaters, and Storage
Cubic feet and liters both measure volume, but they come from completely different measurement systems and show up in different contexts. Cubic feet is the default in American appliance specs, HVAC, and real estate. Liters dominate in aquarium keeping, chemistry, cooking, and most of the world outside the US. When a product spec lists capacity in cubic feet but you need liters — or vice versa — you need the conversion.
The Volume Converter handles this automatically. This article covers the conversion factor, the practical contexts where it comes up, and a set of reference values for common container sizes.
The Conversion Factor
1 cubic foot = 28.3168 liters
So to convert cubic feet to liters, multiply by 28.3168. To go the other direction, divide by 28.3168 (or multiply by 0.03531).
| Cubic feet | Liters |
|---|---|
| 0.5 ft³ | 14.2 L |
| 1 ft³ | 28.3 L |
| 1.5 ft³ | 42.5 L |
| 2 ft³ | 56.6 L |
| 3 ft³ | 84.9 L |
| 4 ft³ | 113.3 L |
| 5 ft³ | 141.6 L |
| 6 ft³ | 169.9 L |
| 7 ft³ | 198.2 L |
| 8 ft³ | 226.5 L |
| 10 ft³ | 283.2 L |
| 15 ft³ | 424.8 L |
| 20 ft³ | 566.3 L |
Where the conversion comes from: 1 foot = 0.3048 meters exactly. 1 cubic foot = 0.3048³ cubic meters = 0.0283168 m³. Since 1 cubic meter = 1,000 liters, 1 cubic foot = 28.3168 liters.
Water Heaters
Water heater capacity in the US is listed in gallons, but the physical dimensions are sometimes described in cubic feet and international models use liters. A 40-gallon water heater holds about 151 liters; a 50-gallon unit holds about 189 liters. In cubic feet, those are 5.35 ft³ and 6.7 ft³.
Tankless water heaters don't store water, so capacity isn't the relevant spec — flow rate in liters per minute (LPM) or gallons per minute (GPM) is. But if you're sizing a storage tank for solar thermal or a backup system, you'll often need to convert between cubic feet (for physical dimensions) and liters (for actual water volume).
The weight of water matters here: 1 liter of water weighs 1 kg. A 200-liter solar storage tank holds 200 kg of water — about 440 lbs. That has structural implications for where it can be installed.
Aquariums and Fish Tanks
Aquariums are sold by gallon in the US and by liter in most other countries. The relationship:
| Tank size (US gallons) | Liters | Cubic feet |
|---|---|---|
| 10 gallons | 37.9 L | 1.34 ft³ |
| 20 gallons | 75.7 L | 2.67 ft³ |
| 29 gallons | 109.8 L | 3.88 ft³ |
| 40 gallons (breeder) | 151.4 L | 5.35 ft³ |
| 55 gallons | 208.2 L | 7.35 ft³ |
| 75 gallons | 283.9 L | 10.03 ft³ |
| 90 gallons | 340.7 L | 12.03 ft³ |
| 125 gallons | 473.2 L | 16.71 ft³ |
The cubic feet figure is useful if you're calculating the weight load on a floor or stand. Water weighs 28.3 kg per cubic foot (or 62.4 lbs per cubic foot). A 75-gallon tank holds 10 cubic feet of water, which is 283 kg (624 lbs) — plus the weight of the tank, substrate, rock, and equipment. Most residential floors handle 150–200 kg/m², so large aquariums need to be placed on or near load-bearing walls.
Refrigerators and Freezers
Refrigerator capacity in the US is listed in cubic feet. European models use liters. The conversion is direct:
| US size | Liters |
|---|---|
| 18 ft³ (compact family fridge) | 510 L |
| 22 ft³ (typical French door) | 623 L |
| 25 ft³ (large side-by-side) | 708 L |
| 28 ft³ (large French door) | 793 L |
| 5 ft³ (chest freezer, small) | 142 L |
| 7 ft³ (chest freezer, medium) | 198 L |
| 15 ft³ (upright freezer, large) | 425 L |
When buying appliances internationally or comparing a US spec sheet to an EU model, this conversion tells you whether you're actually getting the same capacity.
For reference, a typical kitchen fridge in Europe runs 200–350 liters. A US 18 ft³ fridge at 510 liters is larger than most European families buy — partly a cultural difference, partly a difference in how often people shop.
HVAC and Air Volume
In HVAC, airflow is measured in cubic feet per minute (CFM) in the US and liters per second (L/s) in metric systems. The room volume itself is in cubic feet or cubic meters.
1 cubic foot per minute = 0.4719 liters per second 1 liter per second = 2.119 CFM
A room that's 12 × 15 × 9 feet = 1,620 cubic feet = 45,888 liters (45.9 m³). If your ventilation system needs to exchange the air 6 times per hour, that's 9,720 cubic feet per hour = 162 CFM = 76.5 L/s.
Propane and Natural Gas Storage
Propane tanks in the US are measured in gallons, but their physical volume is in cubic feet. A standard 20-lb propane tank (for a backyard grill) holds about 4.7 gallons of liquid propane, which occupies 0.63 cubic feet of space. At room temperature, that liquid propane expands to about 17.8 cubic feet of gas.
For natural gas, flow rates in cubic feet per hour (CFH) need to be converted to liters per hour for international systems:
- 1 CFH = 28.3 liters/hour
- A gas range burner at full heat might use 9,000 BTU/hr, which is about 9 CFH of natural gas = 255 liters/hour
Soil, Mulch, and Compost in Gardening
Bagged soil and mulch in the US are sold by cubic foot or cubic yard. International products use liters. A standard bag of potting mix is often 1 or 1.5 cubic feet — that's 28.3 or 42.5 liters respectively.
This matters when following planting instructions from international sources. A European gardening guide might say "use 50 liters of compost per square meter." That's 1.77 cubic feet, or slightly more than one standard US bag.
For raised beds:
- A 4×4×1 foot raised bed = 16 cubic feet of soil = 453 liters
- A 4×8×1 foot raised bed = 32 cubic feet = 907 liters
- A 4×8×1.5 foot raised bed = 48 cubic feet = 1,359 liters
Quick Mental Approximation
If you need a rough conversion and don't have a calculator: 1 cubic foot is just over 28 liters, or roughly 28 liters per cubic foot.
For mental math, multiply cubic feet by 28 for a quick estimate. This is accurate to within 1.1% — fine for most practical purposes.
Going the other direction: liters ÷ 28 gives cubic feet. For a 200-liter tank: 200 ÷ 28 ≈ 7.1 cubic feet.
For more precise conversions across volume units — including gallons, quarts, milliliters, and cubic centimeters — the Volume Converter covers all combinations in one place.
